1. Field of the Invention
This invention pertains generally to systems for electrical equipment and, more particularly, to such systems that monitor and provide predictive diagnostics for electrical equipment. The invention also pertains to systems that monitor and provide predictive diagnostics for electrical or rotating electrical equipment.
2. Background Information
Today, electrical equipment users are being stretched to do more with less. This translates into lower maintenance budgets and an operating mode of “outages are no longer an option”. Electrical equipment is conventionally maintained on a periodic basis. Known predictive technology for electrical equipment includes thermographic, ultrasonic and partial discharge detection and inspections.
Thermographic and ultrasonic detection are applied at all voltage levels, while partial discharge detection is applied to medium voltage systems. Ultrasonic and partial discharge inspections detect the presence of low-level arcing or corona, which can increase in some cases and result in electrical insulation damage. Thermographic inspections identify “overheated” electrical connections or electrical components within electrical equipment. Loose or deteriorated electrical connections or electrical components will operate at higher temperatures and can be detected when viewing the infrared spectrum of light, visible via thermograph cameras. The temperature of electrical conductors, including electrical connections and electrical components is directly related to the amount of load current that is being transmitted. Therefore, these inspections must be performed while the electrical equipment is energized and loaded. At the same time, varying electrical loads will result in varying operating temperatures for electrical connections; hence, the level of current loading needs to be factored into the analysis.
Thermographic inspections require the opening of front and rear doors while the electrical equipment is energized. The opening of such doors must be accomplished with extreme care, and in some cases should not be performed due to potential safety risks to personnel. For example, a person removing a panel cannot be certain of the distance between a grounded metal door and an energized bus within an electrical equipment enclosure. If an accidental slip of the door occurs, then a faulted condition could result in extremely close proximity to the individual.
There has been a recent proposal in the sensing of overheated electrical connections or other electrical components. One such proposal allows for remote viewing of the infrared spectrum remotely by a permanently mounted camera. The emphasis on personal safety, and newly proposed arc flash standards, has resulted in greater use of “infrared-windows” which allows viewing of infrared radiation through pre-installed infrared-ports. For example, a known thermographic camera provides a “UL recognized latched-port” (⅝ in.) opening to allow an infrared camera's relatively wide-angle to view the inside of the electrical equipment without opening the outer doors.
Another proposal applies permanent temperature sensors to electrical connections or other energized locations and wirelessly transmits the measured temperature to a receiver, which is then connected to a computer for trending, alarming and analysis. Such permanent temperature sensors may operate from internal batteries and, therefore, require that the batteries be changed, which is only possible by a complete shutdown of the electrical equipment. These additional shutdowns to maintain the integrity of the temperature monitoring system is not preferred by end users, which need to operate for relatively longer periods of time at greater levels of reliability. These known systems also do not correlate measured temperatures to other parameters and, thus, do not provide indications of required maintenance based on temperatures or other factors such as dust, smoke and humidity, which appear normal in absolute values, but are actually high, based on historical trended levels, or high for the level of current flow through such electrical connections or other electrical components.
U.S. Pat. No. 5,485,491 discloses an online system for diagnosing operating conditions of a motor, in order to determine when motor maintenance is required. Motor sensors monitor various physical parameters (e.g., non-electrical or insulation-related conditions) and produce corresponding electrical signals. Signal converters transform the electrical signals to corresponding digital values. These values are collected by a processor which compares the values, or a trend of the values, with predetermined baseline values, or trends, associated with a newly manufactured or refurbished motor. The processor then makes recommendations for a motor maintenance interval, in order to provide optimum motor performance and availability at minimum cost and downtime. The motor maintenance interval is a specific time or, alternatively, a more general time, such as the time of the next scheduled refueling outage. In the case of a reactor coolant pump (RCP) motor within a nuclear containment vessel, an intermediate data storage device collects the digital values corresponding to the electrical signals and communicates the digital values to a processor which is remotely located (e.g., beyond a biological barrier, beyond the containment vessel, at an off-site location, etc.) from the RCP motor.
There is room for improvement in systems for electrical equipment.
There is also room for improvement in systems for electrical or rotating electrical equipment.